Carbon dioxide scrubber and breathing diaphragm assembly for diving apparatus

ABSTRACT

A compact carbon dioxide scrubber and breathing diaphragm assembly for a closed circuit breathing system in which exhaled air is channeled by a baffle system over a moisture absorbant material and through a replaceable annular cartridge containing a carbon dioxide removal chemical in such a way that the chemical cartridge is blanketed by the exhaled or expelled air and is insulated from surrounding cold water. Uniform flow through the chemical cartridge is assured by providing high unit area water repellent filters at the top and bottom of the cartridge. Because of the large total area exposed to the flow of expelled air, there is a minimum pressure drop which is virtually unnoticeable to the diver and because of the water repellancy, water or moisture in the exhaled air does not collect upon and form blockages to decrease the effective area exposed to the flow of expelled air. Breathing circuit gases pass into a pressure equalization chamber formed by a diaphragm assembly which accepts that volume of gas in the same fashion as breathing bags which are occasionally used with semi-closed equipment. As the diver descends, water pressure exerts a force on the diaphragm which moves it in a direction to reduce the volume of gas until a valve is tripped permitting the entrance of a diluent or inert gas. During ascents, when water pressure decreases, this same diaphragm surface moves outwardly to expand the volume until a bypass-check valve is opened which permits exhaust of pressure balancing quantities of gas contained in the chamber. This pressure equalization chamber and diaphragm therefore are formed as parts of the same scrubber assembly thus producing a very compact unit which may be closely positioned relative to the lungs of the user and which may be disassembled for replacement of the carbon dioxide scrubber cartridge as well as permitting visual inspection and/or repair of other components of the device. Consult the specification for other features and details.

United States Patent 1 Parker et al.

154] CARBON DIOXIDE SCRUBBER AND BREATHING DIAPHRAGM ASSEMBLY FOR DIVING APPARATUS [75] Inventors: Frederick A. Parker, Broomall, Pa.;

Charles J. Soult, Willingboro, NJ.

[73] Assignee: Biomarine Industries, Inc.

[22] Filed: ,Ian. 28, I970 21 Appl. No.2 6,387

[52] U.S. Cl. ..55/316, 23/284, 55/498, 128/142.2, 128/191 [51] Int. Cl. ..BOId 50/00 [58] Field of Search ..'.55/3l6, 385, 482, 485, 498, 55/516, 524; 23/284; 128/l42.2, 191

[56] References Cited UNITED STATES PATENTS 2,284,964 6/1942 Mautz et a1 l28/145.8 2,830,583 4/1958 Finney et a1 ..128/142 3,000,191 9/1961 Stark ..55/387 3,028,859 4/1962 7 Mitchell... 128/140 R 3,066,462 12/1962 Yap et al. ..55/524 3,252,458 5/1966 Krasberg ..128/147 3,277,890 10/1966 Warncke ..128/142 3,480,011 ll/1969 Cousteau ...128/l42.2 3,572,014 3/1971 Hansen ..55/387 3,575,167 4/1971 Michielson ..55/482 3,577,988 5/1971 Jones ...l28/142.7 1,983,475 12/1934 Lemoine 128/191 R 3,556,098 1/1971 Kanwisher et a1. ..128/142 2,671,528 3/1954 Gross ..55/316 3,326,212 6/1967 Phillips..... ...l28/147 3,353,339 11/1967 Walter ..55/316 OTHER PUBLICATIONS Primary Examiner- Bernard Nozick A ttorney-Beveridge & De Grandi [45] Jan. 16, 1973 [5 7] ABSTRACT A compact carbon dioxide scrubber and breathing diaphragm assembly for a closed circuit breathing system in which exhaled air is channeled by a baffle system over a moisture absorbant material and through a replaceable annular cartridge containing a carbon dioxide removal chemical in such a way that the chemical cartridge is blanketed by the exhaled or expelled air and is insulated from surrounding cold water. Uniform flow through the chemical cartridge is assured by providing high unit area water repellent filters at the top and bottom of the cartridge. Because of the large total area exposed to the flow of expelled air, there is a minimum pressure drop which is virtually unnoticeable to the diver and because of the water repellancy, water or moisture in the exhaled air does not collect upon and form blockages to decrease the effective area exposed to the flow of expelled air. Breathing circuit gases pass into a pressure equalization chamber formed by a diaphragm assembly which accepts that volume of gas in the same fashion as breathing bags which are occasionally used with semiclosed equipment. As the diver descends, water pressure exerts a force on the diaphragm which moves it in a direction to reduce the volume of gas until a valve is tripped permitting the entrance of a diluent or inert gas. During ascents, when water pressure decreases, this same diaphragm surface moves outwardly to expand the volume until a bypass-check valve is opened which pennits exhaust of pressure balancing quantities of gas contained in the chamber. This pressure equalization chamber and diaphragm therefore are formed as parts of the same scrubber assembly thus producing a very compact unit which may be closely positioned relative to the lungs of the user and which may be disassembled for replacement of the carbon dioxide scrubber cartridge as well as permitting visual inspection and/or repair of other components of the device. Consult the specification for other features and details.

14 Claims, 6 Drawing Figures SHEET 1 BF 2 l flk.

PATENTED JAN 16 I975 INVENTORS FREDERICK A. PARKER CHARLES J. SOULT llllllllllllllllllllllll |Il|l||.\

ATTORNEYS PATENTEUJAN 16 1915 SHEEI 2 BF 2 INHALE INVENTORS FREDERICK A. PARKER CHARLES J. SOULT CARBON DIOXIDE SCRUBBER AND BREATHING DIAPHRAGM ASSEMBLY FOR DIVING APPARATUS This invention in general relates to under water breathing apparatus, and in particular to a compact carbon dioxide scrubber or remover and breathing diaphragm assembly for use in closed circuit or semiclosed circuit self-contained under water breathing systems.

In self-contained under water breathing apparatus, the diver is provided with a mouth piece or breathing mask and a breathing circuit connected to the mouth piece having check valves for controlling the directional flow of exhale and inhale gases, such breathing circuits usually including a carbon dioxide removal chemical (as for example Baralyme) and sensors for sensing the partial oxygen pressure of the gases in the breathing system to produce a control signal for admitting more or less oxygen from a supply to the breathing circuit. Such systems may further include breathing bags or like devices which are responsive to the depths of the diver in water to admit more or less of a diluent gas which may be helium or heliox (a mixture of helium and oxygen); Usually, the breathing bags are separate instrumentalities (there are sometimes being two breathing bags) a typical system as thus described being shown in Finney, Jr. US. Pat. No. 2,830,583. The present invention is directed to improvements in the carbon dioxide removal device and the provisions therewith of a breathing diaphragm along with control valves for controlling theingress of diluent or inert gas and the removal or venting of excess gases and includes means for controlling makeup oxygen to the breathing gas circuit.

In accordance with the invention, an annular frame member is provided having upper and lower portions with an exhale gas inlet port at one lateral side of the frame for admitting exhaled gas into a exhaled gas manifold or chamber and an inhale outlet port at a side of a frame member remote from the exhaled gas inlet port. An upper closure member is sealingly clamped to the annular frame to define a sealed housing for a carbon dioxide (CO scrubber cartridge and a lower housing member is sealingly clamped to the annular frame to define a pressure equalization chamber, the clamping may also sealingly clamp a breathing diaphragm in position to define a portion of the pressure equalization chamber.

The carbon dioxide scrubber cartridge is an annular,- donut shaped element which is preferably replaceable and baffles are provided for defining the inhale gas manifold and for constraining the flow of gases through the cartridge into an open space centrally located in the frame with respect to the annularly-shaped cartridge where oxygen sensors are located. A diluent inlet valve is controlled by the movement of the expansion diaphragm to add diluent gas as the diver descends and a vent-check valve is provided in the expansion diaphragm and carried thereby for venting of gas as the diver ascends. Oxygen, under control of the oxygen sensors, is added at a point in the circuit to provide adequate mixing with the gases within the overall scrubber housing and any additional diluent gases which may have been added to the circuit. Further, water collectors are provided in the circuit to remove excess water and the cartridge is provided with high unit area filters at the top and bottom of the cartridge to distribute the air completely over the cartridge and such filters are non-wettable, thereby insuring uniform gas distribution for passage through the cartridge and because the filters are non-wettable, there is no tendency for any moisture or water droplets to spread and form blockages or dams impeding flow of exhale gases through the cartridge to thus maintain a minimum pressure drop which is virtually unnoticeable to the diver. Additionally, such water repellancy inhibits water from contaminating the carbon dioxide removing chemical in the cartridge.

The baffling arrangement is used to control the flow of gas against the water absorbant materials, through the chemicals and the carbon dioxide removable or scrubber assembly, and over the oxygen sensors. Because the carbon dioxide scrubber itself is substantially blanketed by expelled or exhaled air, it is insulated from the surrounding cold water so that the bed of chemicals remain warm and chemical reaction continues unimpeded regardless of water temperature.

The above and other objects, features and advantages of the invention will become more apparent when considered in connection with the following specifications taken in conjunction with the attached drawing wherein:

FIG. 1 is a diagrammatic illustration of a closed circuit breathing system incorporating the invention,

FIG. 2 is a partially cut away side elevational view of the carbon dioxide removal and breathing diaphragm assembly,

FIG. 3 is a cross-sectional view of a device shown in FIG. 2 taken on lines 3-3,

FIG. 4 is a cross-sectional view taken on lines 44 of FIG. 3,

FIG. 5 is a partial cross-sectional view of the carbon dioxide removal cartridge, and

FIG. 6 is a cross-sectional view of the vent-check valve assembly carried by the breathing diaphragm.

FIG. 1 diagrammatically discloses the pertinent portions of a self-contained underwater breathing apparatus in which a mouth piece 10 having conventional exhale and inhale check valves (not shown) leading to exhale pipe 11 and inhale pipe 12, respectively, connected to inhale port 13 and exhale port 14 on combined carbon dioxide removal and breathing diaphragm assembly unit 16. In FIG. 1, for simplicity of illustration, inhale port 13 is shown as being below exhale port 14 and connected directly to the pressure equalization chamber. Combined carbon dioxide removal and breathing diaphragm unit 16 will be described in greater detail hereinafter but in the simplified arrangement shown in FIG. 1, includes a central annular frame member 17 having an inwardly projecting annular divider I8 supporting an annular or donut shaped carbon removal cannister or cartridge 19, through which exhaled gases from exhale pipe 11 are caused to flow. Cover member 15 is sealingly clamped to the upper edge of annular frame 17 by clamp element 150. Water absorbing sponge materials 22 are located on the divider plate 18 to remove moisture from the exhaled gases. Exhaled gases are caused to flow upwardly (in the diagram shown in FIG. 1) through cartridge 19, the baffle means to be described later herein causing an essentially uniform distribution of such gases on the lower surfaces of cartridge 19. The exhaled gases passing through the chemicals in cartridge 19 have carbon dioxide removed therefrom in a conventional manner and on leaving the cartridge 19 pass into a mixing chamber 24 which includes the hole 26 formed by the inner annular walls of cartridge 19. Oxygen sensing means 27 are located in the circular space or cavity 26 in the cartridge and sense the partial oxygen pressure of gases passing through carbon dioxide removal cartridge 19. Such oxygen sensors are of the type disclosed in Rutkowski et al. application Ser. No. 83l,152 filed June 6, 1969. Signals produced by oxygen sensors 27 are processed in a solenoid control circuit 28 which produces signals for operating a solenoid valve 29 to supply oxygen from an oxygen bottle 30, pressure reducer 30R through a line 31 to the mixing chamber 24. Gauge 30m indicates the pressure of gas in bottle 30, and meter device 28m indicates the partial oxygen pressure of gas in the breathing circuit. A safety device in the form of an oxygen bypass valve 32 is provided to permit manual bypassing of the automatic control of oxygen supply in the event of a malfunction in the oxygen control circuitry.

A flexible diaphragm-vent valve assembly 60 is secured along its perimetrical edges to the lower portion of frame member 17 so as to provide a variable volume chamber 59; mounted in chamber 59 is a valve 61 which is controlled by inward movement of diaphragm 60 on descents by the diver, whereby external water pressure applied to the outer surface of diaphragm assembly 60 forces the diaphragm assembly inwardly on inhalation to actuate valve 61 to permit the addition of a diluent gas from a diluent supply bottle 63. As in the case of the oxygen supply, in the event of malfunction of valve 61, a diluent bypass valve 64 is provided to permit the driver to manually control the amount of diluent gas added to the breathing gas circuit. As shown in FIG. 1, the carbon dioxide removal cartridge 19 has a smaller overall diameter than does frame element 17. Moreover, it will be noted that expelled or exhaled gases from the diver essentially sub stantially surround cartridge 19 so as to maintain the temperature essentially constant so that temperature variations do not affect chemical activity in cartridge 19. It will also be noted that the upper cover member which is sealingly secured to frame member 17 has on the interior surface thereof a layer of water absorbing sponge material 40 which, likewise, removes and retains moisture or water which condenses on housing member 15.

With further reference to FIG. 1, it will be noted that the lower cover or housing 41 opposite the flexible diaphragm 60 is a perforated cover member to permit ambient water pressure to be exerted upon diaphragm 60. Perforated lower cover member 41 is clamped to annular frame 17 by clamp 41c and protects diaphragm 60. It will also be noted that diaphragm 60 carries a relief valve assembly 70, the construction of which is described in more detail hereinafter. However, a projection 92 on relief valve assembly 70 is adapted to engage an internal surface portion on cover member 41 so that on ascending, excess pressure within chamber 59 is vented to the exterior of the chamber and the water.

In FIG. 2, parts corresponding to the elements shown in FIG. I carry the same numerals. Annular frame 17 has upper and lower wall portions 17u and 17!. Central support member 53 has a downwardly angled flange 55 welded or otherwise secured along its lower edge to the inner wall surface of frame member 17 and includes an upstanding outer annular wall element 54 welded or otherwise sealingly secured thereto, an inner wall portion 57 which, with wall element 56 and the lower wall surface of the cartridge constitutes an exhaled gas manifold which is directly connected to the exhale port 14 by short exhale port pipe extension Me so that exhale gases are directed from a lateral direction into the manifold and over water absorbant sponge or foam material 22 which is supported on or rests on element 56. Diluent or inert gas is supplied through a pipe 61p to diluent valve 61 which admits diluent gas into the expansion chamber upon vent-check valve engaging spring biased push button 61v which actuates or opens valve 61. Downwardly angled flange 55 may have holes 55H therein to permit gas to flow from the lower portion of the equalization chamber to the annular space leading to inhale port 13.

Cartridge 19 is shown in cross-section in FIG. 5 and has a lower wall element 65 provided with an annular series of perforations 66 which serves as a baffle to cause exhale gases to flow over water absorber 22 and at the same time to achieve a uniform distribution of exhaled gases on the lower surface of filter element 67. It will be noted that wall element 65 is shaped to be spaced away from the outer surface of filter element 67 to permit free flow of exhaled gases in the space between wall 65 and filter element 67. Cartridge 19 is mounted on the upper edges of annular wall- 54 and annular wall portion 57 and as shown in FIG. 5 is provided with sealing or gasket means 68a and 68b which prevent leakage of exhaled gases out of the exhaled gas manifold and constrains all of the gases to pass through the cartridge (such sealing gaskets not being shown in FIG. 2).

With further reference to FIG. 5, cartridge 19 is constituted by an inner annular wall i and an outer annular wall 750 and an upper wall element 75 having perforations 75p therein for permitting free flow of exhaled gases after having passed through the carbon dioxide removing chemicals (soda lime, Baralyme, lithium hydroxide, etc.). An upper filter element 69 closes off the upper end of cartridge 19 to define the space between filter element 67 and 69 and inner and outer wall elements 75: and 750 which receive the carbon dioxide removing chemical. Filter elements 67 and 69 are high unit area filters made from a material which is water repellant or non-wettable and cause the air to be distributed completely and essentially uniformly over the cartridge, thus insuring uniform flow through the chemicals contained therein. Because of the water repellancy property of filters 67, water or moisture not picked up by moisture absorbers 22, which does contact filter 67 do not form dams or blockages to impede the passage of air thus eliminating potential channeling effects found in prior art carbon dioxide removal cannisters. Although the filters are of high efficiency, the large total area of these filters in relation to the cross-sectional areas of the breathing gas circuit provides a minimum pressure drop which is virtually unnoticeable to the diver. A suitable non-wettable porous material for filters 67 and 69 is a material marketed under the trademark Porex."

It will be noted that the cartridge 19 is smaller in outside diameter than is the diameter of housing or cover 15. Thus, the carbon dioxide removal cartridge will be completely blanketed by expelled air and is thus insulated from surrounding cold water so that the chemical bed remains warm and chemical reaction continues unimpeded regardless of water temperature. Furthermore, because the wall temperature remains relatively warm moisture will not tend to conduce on the inner surface (and thereby soak the chemical) as it would were the exterior surface of the cannister exposed to cold ambient water. Wall member'55 may be provided with a series of perforations to remove or avoid having volumes of air which do not move through the unit and a pipe 95 between the annular space between cartridge 19 and frame 17 and the inner space 26 is provided to assure free flow and mixing of gases between these spaces.

As shown in FIGS. 3 and 4, oxygen may be admitted in the annular space between the cartridge and the outer wall portion of frame element 17. Water absorber 40, in addition to collecting water condensing on the inner surfaces of cover member also provides some insulation for the chemicals in cartridge 19.

Cartridge 19 is held in place by release clamps (not shown) so that after extended use or after inadvertent flooding of the system, cover 15 may be removed and the entire cartridge replaced. Alternatively, outer wall 750 may be provided with removable plugs or caps (not shown) to permit easy removal of spent chemicals and otherwise restore the cartridge for further use. It is also contemplated that the casing of cartridge 19 be constructed of inexpensive plastic moldings so that it may be disposable.

When a relatively large amount of water penetrates the cartridge, it becomes useless so most prior art closed or semiclosed breathing systems cannot be buddy breathed e.g. alternate use of a common mouthpiece by two or more divers because water enters the system during passage of the mouthpiece between divers. The scrubber-diaphragm assembly of the present invention, by providing water absorbers 22 and 40 and non-wettable or water repellant filters 67 and 69 on cartridge 19, small amounts of water entering the system through the mouthpiece is prevented from adversely affecting the system and rendering it useless.

In FIG. 4 exhale gas flow is indicated generally by arrows E and inhale gas flow is generally indicated by arrows I.

There may be several oxygen sensors 27 (for safety purposes) in space 24. Oxygen is added to the inhale gas circuit at a point where the reading obtained by the oxygen sensors is essentially that of the exhaled gas after having passed through cartridge 19 and oxygen added at a point to provide adequate mixing of the makeup oxygen with such gas and any diluent gas which may have been added. Manually operated bypass valves 32 and 64 are provided to permit the diver to add oxygen or diluent gases if the need arises.

BREATHING DIAPHRAGM-VENT VALVE ASSEMBLY The diaphragm-vent valve assembly is shown in FIG. 6. The diaphragm per se is a flexible rubber member 61 having a perimetrical edge portion 62 which is adapted to be sealingly clamped by ring claim 58c to the peripheral flange on depending the central frame wall member and a flange on perforated cover member 41.

Vent-check valve assembly is located centrally of diaphragm 61 and includes a support plate 71 which is bonded to the upper surface of diaphragm 61 by an adhesive which is spread uniformly between the two contacting surfaces. A hole or aperture 72 in support plate member 71 has passing therethrough threaded portion 73 of valve body 74. Threadably engaged with the threaded portion 73 of valve body 74 is a base plate member 76 which has a peripheral flange member 77 and an annular groove 78 in which is fitted an O ring 79 so that when base plate member 76 is threaded down in tight engagement with valve body portion 73, there a water tight seal is formed. Base plate member 76 has a plurality of apertures or openings 80 over which fits a flexible rubber check valve element 82 so that water from exterior of the diaphragm 61 is prevented from entering into the expansion chamber per se. Check valve element 82 has a small raised portion 83 over which is fitted a spring 84.

Valve seat member 86 has a recess 87 in the central portion thereof which receives spring 84 such that spring 84 urges check valve element 82 upwardly (as seen in FIG. 6) and valve seat element 86 outwardly or downwardly. An annular V-shaped groove 88 is formed on the outer surface of valve seat flange element 89 and receives an O ring sealing element 90 which provides a seal with inwardly projecting annular flange 91 of valve body 74. Valve body 74 and valve seat 89 constitutes a vent check valve. It will be noted that valve body 89 has a central projection or button 92 which extends outwardly therefrom so that upon pressing in or depression of valve button 92, as for example when the diver is ascending and the pressure in the expansion chamber is sufficient to move the diaphragm fully outwardly to where button 92 engages valve actuating portion of the housing projecting the diaphragm, water from the exterior of the unit is permitted to enter into the chamber or space between check valve element 82 and the valve seat element 89. If the water pressure is less than the interior gas pressure, check valve 82 will open to permit gases to pass through apertures 80 to the exterior of the device.

We claim:

1. A compact carbon dioxide removal unit for use in the breathing gas circuit means of a self-contained underwater breathing apparatus, comprising in combination an annular frame member, said annular frame member including inner and outer annular walls and an annular plate member joined at its outer periphery to said outer annular wall and at its inner periphery to said inner annular wall,

said outer annular wall including a wall portion depending below said annular plate member, and

a flexible diaphragm extending across said frame member and sealingly secured along its peripheral edge to the lower edge of said depending portion of said outer annular wall to thereby define a pressure equalization chamber in said breathing gas circuit,

an apertured plate member secured in spaced relation on said annular plate member to define an annular exhale gas manifold,

means forming a passageway to said annular exhale manifold for exhaled gases for said breathing gas circuit means,

an annular carbon'dioxide removal means containing granular chemical means for removing carbon dioxide from said exhale gases, said annular carbon dioxide removal means having opposed inlet and outlet surfaces which are substantially equal in surface area to said annular exhale gas manifold so that there is a minimum pressure drop by said carbon dioxide removal means to flow of breathing gas in said breathing circuit,

means releasably securing said annular carbon dioxide removal means in spaced relation on said apertured plate member to cause exhaled gas to be applied to the entire inlet surface of said carbon dioxide removal means facing said apertured plate member,

closure means releasably secured to the upper edge of said outer annular wall member,

means for supplying make up oxygen to condition gases passing through said carbon dioxide removal means for rebreathing in said breathing gas circuit, and

outlet means passing'through said outer annular wall for passing conditioned gas to said breathing circuit.

2. The invention defined in claim 1 wherein said carbon dioxide removal means is an annular cartridge having an outside diameter which is less than the diameter of said outer annular wall to define an annular space filled with breathing gas to insulate said cartridge from ambient water temperature.

3. The invention defined in claim 1 including means in said annular gas manifold for removing water from exhaled gases.

4. The invention defined in claim 1 including a source of diluent gas, valve means connected to said source of a diluent gas for admitting a diluent gas to said breathing gas circuit, and

plate means on said diaphragm for engaging and actuating said valve means to admit diluent gas on an increase in ambient water pressure.

5. The invention defined in claim 4 including vent valve means carried by said flexible diaphragm, said vent valve means including,

a support plate secured to and moved with said diaphragm in response to exhalation and variations in ambient water pressure, said support plate being constituted by said plate means on said diaphragm,

a valve body secured to said support plate, said valve body having a central opening therein,

a movable valve element over said central opening in said valve body,

spring means biasing said valve element in a direction to close said central opening,

a projection on said valve element, and

means connected to said outer annular frame for engaging said projection on said movable valve element when gas pressure causes said diaphragm to move outwardly to permit gas to be vented to the 5 water.

6. The invention defined in claim 5 including check valve means between said vent valve means and the gas in said pressure equalization chamber.

7. The invention defined in claim 6 wherein said check valve means comprises an apertured cup-shaped member secured to said valve body member, and

a flexible disc closing the apertures on the water side of said cup-shaped member.

8. The invention defined in claim 1 wherein said means for conditioning includes oxygen sensor means for sensing partial oxygen pressure,

means mounting said sensor means in the space defined by said inner annular walls,

a source of oxygen, and

valve means controlled by said oxygen sensor for controlling the flow of oxygen from said source to said breathing gas circuit.

9. The invention defined in claim 8 wherein said carbon dioxide removal means is an annular cartridge and wherein said cartridge has an outside diameter which is less than the diameter of said outside annular wall and wherein oxygen from said source is introduced into said breathing gas circuit in the annular space between said cartridge and said outer annular wall.

10. In a self-contained underwater breathing system having a breathing gas circuit means including an exhalation gas circuit means portion, an inhalation gas circuit means portion and a gas regenerator circuit meansportion, the improvements in said gas regenerator circuit means portion comprising,

annular housing portion member including a divider plate member extending across the annular housing member and having an outer annular wall extending on each side of said divider plate member,

a cartridge on one side of said divider plate member,

said cartridge containing a granular carbon dioxide removal chemical,

baffle means positioned between said granular carbon dioxide removal chemical and said divider plate for causing exhaled gases to be substantially uniformly distributed over the surface of said granular carbon dioxide removal chemical facing said baffle means, said cartridge having a large inlet surface contiguous to and substantially equal in surface area to said baffle means and a corresponding outlet surface opposite said inlet surface,

a pan shaped housing member, means sealingly joining said housing member to said annular housing portion member,

a flexible diaphragm sealingly secured along its peripheral edge to and extending across said annular housing portion member on said outer annular wall member between the cartridge and pan,

conduit means leading from a supply of a diluent gas under pressure to said breathing gas circuit means,

valve means actuated on movement of said diaphragm on descent to actuate said valve means to permit addition of diluent gas to said breathing gas circuit means,

oxygen sensor means down stream of said annular cartridge for sensing the partial oxygen pressure in said gas circuit, and

oxygen supply means controlled by said sensing means for supplying oxygen to said breathing gas circuit means.

11. In a self-contained underwater breathing gas system including exhale and inhale gas circuit means, and an exhale gas regenerator connecting said exhale gas circuit means to said inhale gas circuit means, improvements in said exhale gas regenerator comprising,

a water tight housing,

an annular exhale gas manifold in said housing,

means connected to said manifold to receive exhale gases from said exhale gas circuit and introduce said exhale gases to said manifold in a direction normal to the axis thereof,

an annular carbon dioxide removing chamber in said housing, said chamber containing an annular bed of carbon dioxide removing chemical, said bed of carbon dioxide removing chemical being positioned in said housing with its axis generally parallel to the axis of said manifold and perpendicular to the plane of the back of a user having an end surface area contiguous and exposed to and of substantially equal area as said manifold,

annular housing means in said housing supporting said bed of carbon dioxide removing chemical in contiguous co-ax'ial relation with respect to said annular exhale gas manifold including means whereby exhale gas from said manifold is directed axially through said annular bed of carbon dioxide removing chemical,

oxygen sensing means in said water tight housing downstream of the bed of chemical for sensing oxygen content of exhale gas passed through said annular cartridge, and

means controlled by said oxygen sensing means for admitting oxygen to exhale gas passed through said annular bed of carbon dioxide removing chemical at a position remote from said oxygen sensing means.

12. The invention defined in claim 11 wherein said gas manifold includes means for removing moisture from exhale gases, and

wherein said carbon dioxide removing means includes a water repellent, high unit area filter, said filter having a surface area substantially co-extensive with the surface area of said manifold so that there is a minimum gas pressure drop thereacross.

13. The invention defined in claim 11 wherein said water-tight housing is substantially circular in crosssection and has a diameter larger than the outside diameter of said annular housing supporting said carbon dioxide removing means to thereby provide an air space between said annular housing and said watertight housing.

14. The invention defined in claim 13 wherein oxygen under control of said oxygen sensing means is admitted into said air space between said carbon dioxide removing means and said water-tight housing. 

1. A compact carbon dioxide removal unit for use in the breathing gas circuit means of a self-contained underwater breathing apparatus, comprising in combination an annular frame member, said annular frame member including inner and outer annular walls and an annular plate member joined at its outer periphery to said outer annular wall and at its inner periphery to said inner annular wall, said outer annular wall including a wall portion depending below said annular plate member, and a flexible diaphragm extending across said frame member and sealingly secured along its peripheral edge to the lower edge of said depending portion of said outer annular wall to thereby define a pressure equalization chamber in said breathing gas circuit, an apertured plate member secured in spaced relation on said annular plate member to define an annular exhale gas manifold, means forming a passageway to said annular exhale manifold for exhaled gases for said breathing gas circuit means, an annular carbon dioxide removal means containing granular chemical means for removing carbon dioxide from said exhale gases, said annular carbon dioxide removal means having opposed inlet and outlet surfaces which are substantially equal in surface area to said annular exhale gas manifold so that there is a minimum pressure drop by said carbon dioxide removal means to flow of breathing gas in said breathing circuit, means releasably securing said annular carbon dioxide removal means in spaced relation on said apertured plate member to cause exhaled gas to be applied to the entire inlet surface of said carbon dioxide removal means facing said apertured plate member, closure means releasably secured to the upper edge of saId outer annular wall member, means for supplying make up oxygen to condition gases passing through said carbon dioxide removal means for rebreathing in said breathing gas circuit, and outlet means passing through said outer annular wall for passing conditioned gas to said breathing circuit.
 2. The invention defined in claim 1 wherein said carbon dioxide removal means is an annular cartridge having an outside diameter which is less than the diameter of said outer annular wall to define an annular space filled with breathing gas to insulate said cartridge from ambient water temperature.
 3. The invention defined in claim 1 including means in said annular gas manifold for removing water from exhaled gases.
 4. The invention defined in claim 1 including a source of diluent gas, valve means connected to said source of a diluent gas for admitting a diluent gas to said breathing gas circuit, and plate means on said diaphragm for engaging and actuating said valve means to admit diluent gas on an increase in ambient water pressure.
 5. The invention defined in claim 4 including vent valve means carried by said flexible diaphragm, said vent valve means including, a support plate secured to and moved with said diaphragm in response to exhalation and variations in ambient water pressure, said support plate being constituted by said plate means on said diaphragm, a valve body secured to said support plate, said valve body having a central opening therein, a movable valve element over said central opening in said valve body, spring means biasing said valve element in a direction to close said central opening, a projection on said valve element, and means connected to said outer annular frame for engaging said projection on said movable valve element when gas pressure causes said diaphragm to move outwardly to permit gas to be vented to the water.
 6. The invention defined in claim 5 including check valve means between said vent valve means and the gas in said pressure equalization chamber.
 7. The invention defined in claim 6 wherein said check valve means comprises an apertured cup-shaped member secured to said valve body member, and a flexible disc closing the apertures on the water side of said cup-shaped member.
 8. The invention defined in claim 1 wherein said means for conditioning includes oxygen sensor means for sensing partial oxygen pressure, means mounting said sensor means in the space defined by said inner annular walls, a source of oxygen, and valve means controlled by said oxygen sensor for controlling the flow of oxygen from said source to said breathing gas circuit.
 9. The invention defined in claim 8 wherein said carbon dioxide removal means is an annular cartridge and wherein said cartridge has an outside diameter which is less than the diameter of said outside annular wall and wherein oxygen from said source is introduced into said breathing gas circuit in the annular space between said cartridge and said outer annular wall.
 10. In a self-contained underwater breathing system having a breathing gas circuit means including an exhalation gas circuit means portion, an inhalation gas circuit means portion and a gas regenerator circuit means portion, the improvements in said gas regenerator circuit means portion comprising, annular housing portion member including a divider plate member extending across the annular housing member and having an outer annular wall extending on each side of said divider plate member, a cartridge on one side of said divider plate member, said cartridge containing a granular carbon dioxide removal chemical, baffle means positioned between said granular carbon dioxide removal chemical and said divider plate for causing exhaled gases to be substantially uniformly distributed over the surface of said granular carbon dioxide removal chemical facing said baffle means, said cartridge having a large inlet surface contiguous to and substantially equal iN surface area to said baffle means and a corresponding outlet surface opposite said inlet surface, a pan shaped housing member, means sealingly joining said housing member to said annular housing portion member, a flexible diaphragm sealingly secured along its peripheral edge to and extending across said annular housing portion member on said outer annular wall member between the cartridge and pan, conduit means leading from a supply of a diluent gas under pressure to said breathing gas circuit means, valve means actuated on movement of said diaphragm on descent to actuate said valve means to permit addition of diluent gas to said breathing gas circuit means, oxygen sensor means down stream of said annular cartridge for sensing the partial oxygen pressure in said gas circuit, and oxygen supply means controlled by said sensing means for supplying oxygen to said breathing gas circuit means.
 11. In a self-contained underwater breathing gas system including exhale and inhale gas circuit means, and an exhale gas regenerator connecting said exhale gas circuit means to said inhale gas circuit means, improvements in said exhale gas regenerator comprising, a water tight housing, an annular exhale gas manifold in said housing, means connected to said manifold to receive exhale gases from said exhale gas circuit and introduce said exhale gases to said manifold in a direction normal to the axis thereof, an annular carbon dioxide removing chamber in said housing, said chamber containing an annular bed of carbon dioxide removing chemical, said bed of carbon dioxide removing chemical being positioned in said housing with its axis generally parallel to the axis of said manifold and perpendicular to the plane of the back of a user having an end surface area contiguous and exposed to and of substantially equal area as said manifold, annular housing means in said housing supporting said bed of carbon dioxide removing chemical in contiguous co-axial relation with respect to said annular exhale gas manifold including means whereby exhale gas from said manifold is directed axially through said annular bed of carbon dioxide removing chemical, oxygen sensing means in said water tight housing downstream of the bed of chemical for sensing oxygen content of exhale gas passed through said annular cartridge, and means controlled by said oxygen sensing means for admitting oxygen to exhale gas passed through said annular bed of carbon dioxide removing chemical at a position remote from said oxygen sensing means.
 12. The invention defined in claim 11 wherein said gas manifold includes means for removing moisture from exhale gases, and wherein said carbon dioxide removing means includes a water repellent, high unit area filter, said filter having a surface area substantially co-extensive with the surface area of said manifold so that there is a minimum gas pressure drop thereacross.
 13. The invention defined in claim 11 wherein said water-tight housing is substantially circular in cross-section and has a diameter larger than the outside diameter of said annular housing supporting said carbon dioxide removing means to thereby provide an air space between said annular housing and said water-tight housing.
 14. The invention defined in claim 13 wherein oxygen under control of said oxygen sensing means is admitted into said air space between said carbon dioxide removing means and said water-tight housing. 